Device for producing a gas-liquid mixture in the vicinity of cutting tools

ABSTRACT

In a device for producing a gas-liquid mixture and, in particular, air-water mixture in the region of cutting tools, particularly chisels, arranged on at least one cutter head ( 10 ) rotationally mounted on a cutter arm ( 5 ) of a cutting machine ( 1 ), including at least one nozzle pair comprised of a nozzle ( 14 ) for ejecting a gas jet and a nozzle ( 13 ) for ejecting a liquid jet, wherein the axes ( 17, 18 ) of the nozzles ( 13, 14 ) of a nozzle pair are oriented in a manner that the jets impinge on each other at a distance from the outlet openings of the nozzles, the axes ( 17, 18 ) of the nozzles ( 13, 14 ) of a nozzle pair form an angle with each other of between 45 and 135°, preferably between 75 and 85°.

The invention relates to a device for producing a gas-liquid mixtureand, in particular, air-water mixture in the region of cutting tools,particularly chisels, arranged on at least one cutter head or cutterdrum rotationally mounted on a cutter arm of a cutting machine,including at least one nozzle pair comprised of a nozzle for ejecting agas jet and a nozzle for ejecting a liquid jet, the axes of the nozzlesof a nozzle pair being oriented in a manner that the jets impinge oneach other at a distance from the outlet openings of said nozzles.

Devices of the initially defined kind, for instance, are to be takenfrom DE 19951848 A1. Moreover, a number of devices are known, in whichcooling water or water-air mixtures are introduced into the cuttingtraces of cutters so as to enable sparks to be extinguished and thecutting trace behind the chisel to be cooled. Such nozzling realized bythe aid of air and/or water is, for instance, known as single-chiselnozzling, in which the release of the nozzle is controlled as functionof a displacement movement of a chisel caused by reaction forces.Alternatively, devices for forming a more or less uniform spray misthave been proposed, which direct the spray jets onto the cutting unit toproduce a spray mist enveloping the cutting unit. A device of this typeis, for instance, known from DE 3609754 A1.

Nozzling means for cutter head chisels in the first place serve thepurpose of dust abatement and to reduce the risk of ignition of anescaping methane-gas-air mixture. Cooling of the chisel naturally alsoaims to reduce wear. In that case, nozzling is often realized by the aidof a gas-liquid mixture and, in particular, air-water mixture, wherebyseveral methods have become known to produce such air-water mixtures. Tothis end, in the method known from DE 19532459, a spray mist jet isproduced of air and water by atomization, which spray mist jet is usedto act upon the chisels and/or cutting traces in order to preventscarfing in the region of the cutting area. To produce an air-watermixture, DE 2816797 A1 proposes to provide in the air outlet channelsradial bores communicating with a water-conducting volume so as to causewater and air to exit the nozzles in the atomized state. The axes ofthose nozzles are oriented towards that cutter head side on which thechisels come out from the rock. From DE 19851620 A1, a nozzling systemhas become known, in which the spraying nozzles are configured as mistprojectors into whose projector bores, which are connected with thecompressed-air-fed air chamber, a water injection nozzle fed with waterunder pressure each opens to produce a water jet extending in thelongitudinal direction of the projector bore, the pressure of the waterunder pressure being higher than that of the compressed air.

In the nozzling device according to DE 19951848 A1, from which thepresent invention departs, at least one water nozzle generating a waterjet is associated with an air nozzle in a manner that the air jet andthe water jet contact each other at a distance from the nozzle outletopenings while forming an air-water mixture that acts upon the cutterhead. In that case, the individual nozzles are arranged, and the axes ofsaid nozzles are oriented, in a manner that the air and water jets meeteach other at angles of about 10 to 15°.

The known nozzle systems, however, have in common that quiteconsiderable amounts of water must be supplied to produce water-airmixtures, which involves the disadvantage of the floor being soaked andhence no longer safeguarding the secure and precise displaceability of acutter or advance working machine. The invention, therefore, aims toprovide a device for producing a gas-liquid mixture of the initiallydefined kind, which allows for efficient atomization in the region ofthe cutting units using even small amounts of liquid so as to preventundue soaking. At the same time, as fine an atomization of the liquid aspossible is to be ensured in order to reduce the risk of ignition in theregion of the cutting unit. Finally, the device according to theinvention is to provide sufficient cooling of the cutting tools and, inparticular, chisels despite those small amounts of liquid. To solve thisobject, the device according to the invention, departing from thenozzling device mentioned in the beginning, essentially consists in thatthe axes of the nozzles of a nozzle pair form an angle with each otherof between 45 and 135°, preferably between 75 and 85°. Due to the factthat, unlike with known devices, the liquid and gas nozzles are orientedin a manner that a liquid jet and a gas jet impinge on each other at anangle of between 45 and 135°, particularly effective atomization will beensured while forming a mist having a droplet spectrum that reduces therisk of ignition while simultaneously promoting sufficient cooling ofthe cutting units. Because of the steeper angle of attack between thegas and liquid nozzles, the water jet is more strongly deflected fromits original direction, thus ensuring more effective atomization. Indoing so, it has been shown that a substantial enhancement ofatomization occurs at angles larger than 45°, because in that case thenormal component of one of the jets relative to the other jet is largerthan the parallel direction component.

The spraying performance may be even further enhanced in that the liquidjet meets with the gas jet very close to the outlet of the latter, sincethere the air speed is the highest and particularly high shearing forceswill enter into effect. In a preferred manner, the device according tothe invention is, therefore, further developed such that the crossingpoint of the axes of the nozzles of a nozzle pair is located at adistance of less than 100 mm, preferably less than 50 mm, particularlypreferred about 8 mm, from the nozzle outlet opening of the gas nozzle.

The fact that, according to the invention, the axes of the nozzles of anozzle pair enclose an angle of between 45 and 135° naturally entailsthe risk of the liquid jet piercing the gas jet. In order to preventthis, it is advantageously provided that the outlet angles of the liquidnozzles amount to between 5° and 10°, whereby the liquid nozzles may bedesigned as circular section jet nozzles whose outlet openingspreferably have diameters of about 1 mm. With such a configuration, thepunctual impingement of the liquid jet on the gas jet will be preventedand a particularly uniform propagation of the liquid jet will bepromoted, so that a fine mist having a uniform droplet distribution anddroplet size distribution will be obtained.

In the region of the gas nozzle, optimization will be ensured in thatthe diameters of the outlet openings of the gas nozzles are at last 3 mmand, preferably, about 5 mm, wherein it may further be envisaged toconfigure the gas nozzle with a whirl chamber arranged upstream of saidoutlet opening to generate turbulent flows. Such a whirl chamberarranged upstream of the outlet opening allows turbulences to form in amanner that the gas jet will leave the nozzle as a turbulent flow, orwith a twist. The efficacy of spraying will, thus, be further enhancedand the droplet diameter of the mist will be further reduced.

The individual parameters of the forming mist can be influenced byadjusting the gas supply pressure or liquid supply pressure,respectively, particularly favorable properties having been observed atadjusted gas pressures of 0.6 to 1.5 bar. In an advantageous manner, theconfiguration is therefore further developed such that the gas nozzlesare designed for a gas supply pressure of 0.6 to 1.5 bar and the liquidnozzles are designed for a liquid supply pressure of 4 to 5 bar.

By the device according to the invention an extremely fine mist isformed in the region of the cutting tools, which mist also ensures thecooling of the tools in addition to reducing the risk of ignition. Tothis end, the nozzles are arranged on that side of the cutter head, onwhich the chisels enter the rock. Due to the Cuanda effect, theair-water mixture is effectively conducted through the cutting region soas to ensure such cooling effect within the contact zone and, to a majorextent, even beyond engagement. In order to selectively apply suchcooling effect on the chisels, the configuration advantageously isfurther developed in a manner that the axes of the gas nozzles arearranged to be directed onto the cutting tools and, in particular, tipsof the chisels. The mist is thereby formed with a flow that is directedto the tips of the chisels so as to ensure the selective action on thecutter unit parts subjected to special loads, and provide sufficientcooling despite a reduced amount of liquid.

In order to produce a mist uniformly distributed over the entire lengthof the cutter head or cutter drum, a plurality of nozzle pairs arepreferably arranged on a nozzle assembly connected with the cutter armand extending parallel with the axis of rotation of the cutter head orcutter drum. In order to ensure sufficient mist density, the distance ofneighboring nozzle pairs is advantageously less than 150 mm. In such acase, adequate nozzling of the cutting units will be ensured even ifindividual ones of the nozzles distributedly arranged over the length ofthe cutter head break down, since neighboring nozzle pairs enter intoeffect in the region of the broken-down nozzles on account of thesuitable fanning out of the liquid-gas mixture.

In order to provide an easy adjustability of the nozzling parametersand, in particular, the angles between the axes of the liquid nozzlesand the axes of the gas nozzles, and adapt the same to the respectiveoperating conditions, the configuration is advantageously furtherdeveloped in a manner that the nozzles are pivotally mounted in thenozzle assembly.

The nozzling device according to the invention renders feasible theobtainment of a substantially enhanced atomization of the liquid byobserving optimum spraying conditions so as to reach a reduced risk ofignition, and an excellent extinguishing effect, even with small amountsof liquid. In addition, the visibility to the cutting unit will not beexcessively obscured by the arrangement of the nozzle axes according tothe invention. Since the nozzling system according to the invention alsoaffords efficient dust abatement and chisel cooling, the nozzling systemaccording to the invention may also be employed with socalled dry cutterheads, i.e., cutter heads that are not directly subjected to chiselnozzling.

In the following, the invention will be explained in more detail by wayof an exemplary embodiment schematically illustrated in the drawing.Therein,

FIG. 1 is a side view of an advance working machine including a nozzlingdevice fixed to the cutter drive;

FIG. 2 is a front view of the nozzle block;

FIG. 3 is a section along line III—III of FIG. 2; and

FIG. 4 is a section through an air nozzle.

FIG. 1 depicts a cutting machine 1 which is displaceable by a crawlermechanism 2 on a floor 3. The cutting machine 1 comprises a chargingdevice schematically indicated by 4 and a cutter arm 5 which ispivotable in the horizontal direction about a substantially verticalaxis 6 and articulately connected so as to be pivotable in the verticaldirection about a substantially horizontal axis 7 in the sense of doublearrow 8. The pivot drive in the vertical direction is schematicallyindicated by a hydraulic cylinder piston unit 9. A haulage device isindicated on the rear end of the machine.

The cutter arm 5 carries cutter heads 10, which are rotationally drivenin the sense of arrow 11. In the region of the cutter gear, a nozzleblock 12 is fixed to the cutter arm 5, whose front view is depicted inFIG. 2.

From FIG. 2 it is apparent that a plurality of nozzle pairs are arrangedon the nozzle block 12, each nozzle pair being comprised of a liquid,particularly water, nozzle 13 and a gas, particularly air, nozzle 14.The common water connection is denoted by 15 and the common airconnection is denoted by 16. The nozzle block extends over the width ofthe cutter head and, by the two lateral nozzle block projections 22,even over the left-hand and right-hand roof-section portions of thecutter head. In order to enhance the cooking effect, an additionalnozzle block may be arranged on the lower side of the ranging arm suchthat the chisels will be aftercooled upon retraction from the cuttingregion.

From the sectional view according to FIG. 3, the orientation of thenozzles 13 and 14 of a nozzle pair is apparent. The axes of the nozzlesare denoted by 17 and 18, respectively, and, according to the invention,enclose an angle α of between 45 and 135°, the drawing depicting aparticularly preferred angle of 80°. Furthermore, the nozzles arearranged in a manner that the point of impingement 19 is located at adistance a from the outlet opening of the air nozzle, which distance ispreferably less than 100 mm. In the arrangement depicted in FIG. 3, thedistance a in a particularly preferred manner is 8 mm.

FIG. 4 is an enlarged illustration of the outlet-side portion of the airnozzle 14 with a whirl chamber 21 being arranged upstream of the outletopening 20 to cause the generation of turbulent flows. The innerdiameter b of the air nozzle in a particularly preferred manner is about5 mm.

1. A device for producing a gas-liquid mixture in the vicinity ofcutting tools arranged on at least one cutter head (10) or cutter drumrotationally mounted on a cutter arm (5) of a cutting machine (1),comprising at least one nozzle pair comprised of a nozzle (14) forejecting a gas jet and a nozzle (13) for ejecting a liquid jet, axes(17, 18) of the nozzles (13, 14) of a nozzle pair being oriented in amanner that the jets impinge on each other at a distance from outletopenings of said nozzles (13, 14), wherein the axes (17, 18) of thenozzles (13, 14) of a nozzle pair form an angle with each other ofbetween 45° and 135°, a crossing point of the axes (17, 18) of thenozzles (13, 14) of a nozzle pair is located at a distance of less than100 mm from the outlet opening of the gas nozzle (14), and outlet anglesof liquid nozzles (13) amount to between 5° and 10°.
 2. The deviceaccording to claim 1, wherein liquid nozzles (13) are designed ascircular section jet nozzles whose outlet openings have diameters ofabout 1 mm.
 3. The device according to claim 1, wherein diameters of theoutlet openings of the gas nozzles (14) are at least 3 mm.
 4. The deviceaccording to claim 1, wherein the gas nozzles (14) are configured tocomprise a whirl chamber arranged upstream of said outlet opening togenerate turbulent flows.
 5. The device according to claim 1, whereinthe gas nozzles (14) are designed for a gas supply pressure of 0.6 to1.5 bar and the liquid nozzles (13) are designed for a liquid supplypressure of 4 to 5 bar.
 6. The device according to claim 1, wherein theaxes (18) of the gas nozzles (14) are arranged to be directed onto thecutting tools.
 7. The device according to claim 1, wherein a pluralityof nozzle pairs are arranged on a nozzle assembly (12) connected withthe cutter arm (5) and extending parallel with an axis of rotation (8)of the cutter head (10).
 8. The device according to ciaim 1, whereindistance between neighboring nozzle pairs is less than 150 mm.
 9. Thedevice according to claim 7, wherein the nozzles (13, 14) are pivotallymounted in the nozzle assembly (12).
 10. The device according to claim1, wherein the cutting tools are chisels.
 11. The device according toclaim 1, wherein the axes (17, 18) of the nozzles (13, 14) of a nozzlepair form an angle with each other of between 75° and 85°.
 12. Thedevice according to claim 1 wherein a crossing point of the axes (17,18) of the nozzles (13, 14) of a nozzle pair is located at a distance ofless than 50 mm from the outlet opening of the gas nozzle (14).
 13. Thedevice according to claim 1, wherein a crossing point of the axes (17,18) of the nozzles (13, 14) of a nozzle pair is located at a distance ofabout 8 mm from the outlet opening of the gas nozzle (14).
 14. Thedevice according to claim 1, wherein diameters of the outlet openings ofthe gas nozzles (14) are about 5 mm.
 15. The device according to claim10, wherein the axes (18) of the gas nozzles (14) are arranged to bedirected onto tips of the chisels.